The organization of cells of the cat dorsal horn will be determined with respect to cutaneous input. Extracellular recording will be used to determine the relationship between cell location in dorsal horn and cutaneous receptive field location of the recorded cell. Intracellular recording, in conjunction with injection of Procion dyes, will be used to investigate correlations between physiological properties and cell geometry. An attempt will be made to trace the axonal arborizations of single, characterized dorsal root fibers. If access to an appropriate computer can be arranged, the timing of discharge evoked by controlled cutaneous input will be analyzed, using a variety of stimulus paradigms, to determine properties of the central neuronal network. These studies, in conjunction with techniques presently under development, should lead to a more detailed understanding of physiological and anatomical connectivities in this neuronal network.